Airborne SAR on circular trajectories to reduce layover and shadow effects of urban scenes

Circular synthetic aperture radar (CSAR) can provide a full aspect coverage on interesting scenes in one run. Over the city of Karlsruhe a Ka-band dataset was generated in CSAR mode. The data was focused using subapertures in a step of 1.5°, each SAR image representing the scene from a slightly different aspect. The potential of non-coherent fusion of full aspect coverage to reveal small targets was demonstrated. By a manual selection of the viewing angle, parking cars next to high buildings could be revealed and a full view on selected targets with reduced shadow and overlay effects was shown. We studied the effect of varying aspects on the focused image pixels and developed a first metric to automatically select the best viewing angle to a local scene. Areas containing ground information like grass or asphalt and which are not hidden between high objects could be identified and used to deliver a good aspect view on neighboring areas which suffer from shadowing effects.